From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <SRS0=t4Rs=5I=kvack.org=owner-linux-mm@kernel.org>
X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on
	aws-us-west-2-korg-lkml-1.web.codeaurora.org
X-Spam-Level: 
X-Spam-Status: No, score=-8.4 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED,
	DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,
	MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1
	autolearn=ham autolearn_force=no version=3.4.0
Received: from mail.kernel.org (mail.kernel.org [198.145.29.99])
	by smtp.lore.kernel.org (Postfix) with ESMTP id 1DBF9C4332B
	for <linux-mm@archiver.kernel.org>; Mon, 23 Mar 2020 23:11:59 +0000 (UTC)
Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17])
	by mail.kernel.org (Postfix) with ESMTP id B6BE820409
	for <linux-mm@archiver.kernel.org>; Mon, 23 Mar 2020 23:11:58 +0000 (UTC)
Authentication-Results: mail.kernel.org;
	dkim=pass (2048-bit key) header.d=nvidia.com header.i=@nvidia.com header.b="fr9zaypf"
DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org B6BE820409
Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=nvidia.com
Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org
Received: by kanga.kvack.org (Postfix)
	id 194666B0005; Mon, 23 Mar 2020 19:11:58 -0400 (EDT)
Received: by kanga.kvack.org (Postfix, from userid 40)
	id 145476B0006; Mon, 23 Mar 2020 19:11:58 -0400 (EDT)
X-Delivered-To: int-list-linux-mm@kvack.org
Received: by kanga.kvack.org (Postfix, from userid 63042)
	id 05AF16B0007; Mon, 23 Mar 2020 19:11:58 -0400 (EDT)
X-Delivered-To: linux-mm@kvack.org
Received: from forelay.hostedemail.com (smtprelay0003.hostedemail.com [216.40.44.3])
	by kanga.kvack.org (Postfix) with ESMTP id DF5026B0005
	for <linux-mm@kvack.org>; Mon, 23 Mar 2020 19:11:57 -0400 (EDT)
Received: from smtpin16.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251])
	by forelay01.hostedemail.com (Postfix) with ESMTP id BBFCC1804475A
	for <linux-mm@kvack.org>; Mon, 23 Mar 2020 23:11:57 +0000 (UTC)
X-FDA: 76628176674.16.rose41_110ea73c2041f
X-HE-Tag: rose41_110ea73c2041f
X-Filterd-Recvd-Size: 5267
Received: from hqnvemgate25.nvidia.com (hqnvemgate25.nvidia.com [216.228.121.64])
	by imf36.hostedemail.com (Postfix) with ESMTP
	for <linux-mm@kvack.org>; Mon, 23 Mar 2020 23:11:57 +0000 (UTC)
Received: from hqpgpgate101.nvidia.com (Not Verified[216.228.121.13]) by hqnvemgate25.nvidia.com (using TLS: TLSv1.2, DES-CBC3-SHA)
	id <B5e79420f0000>; Mon, 23 Mar 2020 16:11:11 -0700
Received: from hqmail.nvidia.com ([172.20.161.6])
  by hqpgpgate101.nvidia.com (PGP Universal service);
  Mon, 23 Mar 2020 16:11:55 -0700
X-PGP-Universal: processed;
	by hqpgpgate101.nvidia.com on Mon, 23 Mar 2020 16:11:55 -0700
Received: from [10.2.48.195] (10.124.1.5) by HQMAIL107.nvidia.com
 (172.20.187.13) with Microsoft SMTP Server (TLS) id 15.0.1473.3; Mon, 23 Mar
 2020 23:11:55 +0000
Subject: Re: [PATCHv8 2/2] mm/gup: fix omission of check on FOLL_LONGTERM in
 gup fast path
To: Pingfan Liu <kernelfans@gmail.com>, <linux-mm@kvack.org>
CC: Ira Weiny <ira.weiny@intel.com>, Andrew Morton
	<akpm@linux-foundation.org>, Mike Rapoport <rppt@linux.ibm.com>, Dan Williams
	<dan.j.williams@intel.com>, Matthew Wilcox <willy@infradead.org>, Aneesh
 Kumar K.V <aneesh.kumar@linux.ibm.com>, Christoph Hellwig
	<hch@infradead.org>, Shuah Khan <shuah@kernel.org>, Jason Gunthorpe
	<jgg@ziepe.ca>, <linux-kernel@vger.kernel.org>
References: <1584876733-17405-1-git-send-email-kernelfans@gmail.com>
 <1584876733-17405-3-git-send-email-kernelfans@gmail.com>
X-Nvconfidentiality: public
From: John Hubbard <jhubbard@nvidia.com>
Message-ID: <235271bd-cd64-f6d2-bbe1-43de47196ec6@nvidia.com>
Date: Mon, 23 Mar 2020 16:11:54 -0700
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101
 Thunderbird/68.6.0
MIME-Version: 1.0
In-Reply-To: <1584876733-17405-3-git-send-email-kernelfans@gmail.com>
X-Originating-IP: [10.124.1.5]
X-ClientProxiedBy: HQMAIL105.nvidia.com (172.20.187.12) To
 HQMAIL107.nvidia.com (172.20.187.13)
Content-Type: text/plain; charset="utf-8"; format=flowed
Content-Language: en-US
Content-Transfer-Encoding: 7bit
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=nvidia.com; s=n1;
	t=1585005071; bh=ACQ6FT0G1l2a3dThVlaN/TkjQf2hbh/+Acsn76kMJRY=;
	h=X-PGP-Universal:Subject:To:CC:References:X-Nvconfidentiality:From:
	 Message-ID:Date:User-Agent:MIME-Version:In-Reply-To:
	 X-Originating-IP:X-ClientProxiedBy:Content-Type:Content-Language:
	 Content-Transfer-Encoding;
	b=fr9zaypfHIpSzr4SAWVQqI/Hx9bpIyTBrBOUMwtbZkEKpPE2Whud4ret4t2nWd3/P
	 /d8v4zOtMa87yRMCo3cC191LGi24yNLBf+ILFys0AgoBJG45IYERPucpf0qfHpgxxi
	 dgcog6v4M+eQJdzq6P+UQcxA8ysB0UP34PEJ5CW0NPGUwF/Se6u8tTpWcvnLGxnuEZ
	 vwpbGnbVB7qHGVt7DzpX6JRiM7uTcsA1GiGyiknUkc1DE2lF3qTD9+XEicJpesoYXC
	 SA8Fs1xnVBhTd8tfturNDO5MYjjUT7+aET7Gzt2nHkrLNIH0dl05PHG3+qGxVg0RyP
	 c/lNX1VsT7LJw==
X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4
Sender: owner-linux-mm@kvack.org
Precedence: bulk
X-Loop: owner-majordomo@kvack.org
List-ID: <linux-mm.kvack.org>

On 3/22/20 4:32 AM, Pingfan Liu wrote:
> FOLL_LONGTERM is a special case of FOLL_PIN. It suggests a pin which is
> going to be given to hardware and can't move. It would truncate CMA
> permanently and should be excluded.
> 
> In gup slow path, where
> __gup_longterm_locked->check_and_migrate_cma_pages() handles FOLL_LONGTERM,
> but in fast path, there lacks such a check, which means a possible leak of
> CMA page to longterm pinned.
> 
> Place a check in try_grab_compound_head() in the fast path to fix the leak,
> and if FOLL_LONGTERM happens on CMA, it will fall back to slow path to
> migrate the page.
> 
> Some note about the check:
> Huge page's subpages have the same migrate type due to either
> allocation from a free_list[] or alloc_contig_range() with param
> MIGRATE_MOVABLE. So it is enough to check on a single subpage
> by is_migrate_cma_page(subpage)
> 
> Signed-off-by: Pingfan Liu <kernelfans@gmail.com>
> Reviewed-by: Christoph Hellwig <hch@lst.de>
> Reviewed-by: Jason Gunthorpe <jgg@mellanox.com>
> Cc: Ira Weiny <ira.weiny@intel.com>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: Mike Rapoport <rppt@linux.ibm.com>
> Cc: Dan Williams <dan.j.williams@intel.com>
> Cc: Matthew Wilcox <willy@infradead.org>
> Cc: John Hubbard <jhubbard@nvidia.com>
> Cc: "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>
> Cc: Christoph Hellwig <hch@infradead.org>
> Cc: Shuah Khan <shuah@kernel.org>
> Cc: Jason Gunthorpe <jgg@ziepe.ca>
> To: linux-mm@kvack.org
> Cc: linux-kernel@vger.kernel.org
> ---
>   mm/gup.c | 8 ++++++++
>   1 file changed, 8 insertions(+)
> 
> diff --git a/mm/gup.c b/mm/gup.c
> index 02a95b1..3fe75c4 100644
> --- a/mm/gup.c
> +++ b/mm/gup.c
> @@ -89,6 +89,14 @@ static __maybe_unused struct page *try_grab_compound_head(struct page *page,
>   		int orig_refs = refs;
> 
>   		/*
> +		 * Can't do FOLL_LONGTERM + FOLL_PIN with CMA in the gup fast
> +		 * path, so fail and let the caller fall back to the slow path.
> +		 */
> +		if (unlikely(flags & FOLL_LONGTERM) &&
> +				is_migrate_cma_page(page))
> +			return NULL;
> +
> +		/*


Reviewed-by: John Hubbard <jhubbard@nvidia.com>

thanks,
-- 
John Hubbard
NVIDIA


>   		 * When pinning a compound page of order > 1 (which is what
>   		 * hpage_pincount_available() checks for), use an exact count to
>   		 * track it, via hpage_pincount_add/_sub().
> --
> 2.7.5
> 
>